Magnesium

Magnesium, a mineral present in most foods, is essential for human metabolism and for maintaining the electrical potential in nerve and muscle cells. When associated with widespread malnutrition, especially in alcoholics, a magnesium deficiency results in tremors and convulsions. Magnesium is involved in more than 300 reactions in which food is synthesized to new products, and it is a critical component in the processes that create muscular energy from carbohydrate, protein, and fat.⁶⁸ The adult DRI for magnesium ranges between 310 and 320 milligrams per day for females and 400 and 420 milligrams per day for males. The safe upper limit for magnesium is similar to the DRI but represents the intake from supplement doses only and does not include the amount obtained from foods and water.

It is possible that athletes training in hot and humid environments could lose a relatively large amount of magnesium by sweating. Were this to occur, a magnesium deficiency could, given the importance of magnesium in muscle function processes, cause athletes to underachieve athletically. In one study where magnesium supplements were given to athletes, an improvement in physical performance was shown.⁶⁹ There is some limited evidence that taking magnesium supplements at the level of the DRI may positively affect endurance and strength performance in athletes with blood magnesium levels at the low end of the normal range.^{70, 71} In a study assessing the effect of magnesium supplements (365 milligrams per day) on well-trained marathon runners, the supplements had no impact on performance, did not improve resistance to muscle breakdown, and did not enhance muscle recovery after the race.⁷² With the exception of athletes who are known to reduce total energy intake to maintain or lower body weight (wrestlers, gymnasts, figure skaters), it appears that most male athletes consume the DRI or more, and most female athletes consume at least 60 percent of the magnesium DRI.^{73, 74} The limited number of studies assessing magnesium and performance suggest that this level of intake is sufficient to sustain athletic performance and that supplemental intake does little or nothing to enhance performance when magnesium tissue levels are at or near normal.